1. Field of the Invention
For many years, physical therapists have known instinctively that the best form of therapeutic exercise is movement of a muscle against a resisting force. This has been confirmed experimentally over the past 20 years. Because of the way muscles attach to bones on either side of a joint, and because of the biomechanical properties of muscle fibers, optimal forces change with changing joint angles. When applying manual therapy, it is relatively easy to vary the resisting force. However, tradiational mechanical exercise devices based on springs, weights or friction do not have the ability to adapt their resisting forces easily.
Research into muscle physiology has found exercise against constant resistance (isotonic) or without movement (isometric) less effective in increasing power and endurance of muscles than exercise where a constant velocity is maintained (isokinetic). This insight has found its way from the laboratory into treatment and training settings.
Because of its high cost, present isokinetic equipment is available only in few therapeutic settings and reserved mainly for rehabilitation after sport injuries. Current isokinetic exercise equipment is designed primarily for reciprocating movement and consequently not suitable for continuous exercise such as wheeling and cycling. A recent review of isokinetic exercise can be found in Osterning LR, Isokinetic dynamometry: implications for muscle testing and rehabilitation. Exerc. Sport Sci. Rev. 1986; 14: 45-80.
The present invention provides a simple exercise device, exhibiting isokinetic properties, which can be used in various forms of continuous and reciprocating exercise.
2. Discussion of Prior Art
Perrine (U.S. Pat. No. 3,465,592, Sept. 9, 1969) teaches the first truly isokinetic exercise method and apparatus, giving reference to his earlier inventions. He describes two almost separate inventions. His first embodiment uses the principle of the locked worm gear to absorb the power from the exercising person. The apparatus uses locked worm gears and overrunning clutches. The user moves the gear through an interfacing means. The speed of operation is determined by a motor turning the worm. The whole power, arising both from exercise and the motor, is absorbed in the worm and gear, causing high temperatures and wear. If the worm gear does exhibit significantly negative efficiency, the power required by the reference motor increases, the harder the user exercises. Because of this, the second embodiment, using hydraulic cylinders, is also used commercially. In this embodiment only reciprocating operation is possible over limited angles of operation.
Wilson (U.S. Pat. No. 3,902,480, Sept. 2, 1975). A feedback controlled system utilizing electronic and electromechanical devices as controlled exercising loads for use in isotonic or isokinetic exercising therapy, the equipment affording a wide variety of operating modes.
Flavell (U.S. Pat. No. 3,869,121, Mar. 4, 1975). A proportional resistance exercise servo device. User interfacing means is connected to a drive shaft so that the user applies force to said drive shaft and vice versa. The device applies braking force to the drive shaft as it is rotated in a first direction by user-exerted force on the interfacing means, in a braking mode; and it applies power to drive the drive shaft in a second direction and thereby exerts force on the interfacing means, in a power mode. Direction reversal means automatically stops the braking at a first limit and thereafter applies power thereto, and automatically stops the power at a second limit and thereafter begins braking it. Both the braking and powering are programmed, but feedback alters the program in accordance with the user's performance. Acceleration and deceleration are controlled. Various performance parameters are displayed or recorded.
Proctor (U.S. Pat. No. 4,007,927, Feb. 15, 1977). Is typical for traditional exercise cycles: A stationary frame on a supporting surface carries a handlebar and seat to accommodate a person wishing to exercise. A flywheel above the supporting surface is journalled on the frame for rotation by a pair of pedals; and an adjustment knob on the frame enables the rider to control the amount of braking resistance exerted on the flywheel by a pair of brake shoes.
Flavell (U.S. Pat. No. 4,082,267, Apr. 4, 1978). A proportioned resistance exercising apparatus capable of exercising two limbs synchronously or separately with a single resistance mechanism. Two limb-engageable drive input devices are connected through one-way clutches to a single rotary shaft, which is, in turn, drivingly connected to the proportioned isokinetic resistance-producing mechanism.
Snellen (Snellen JW; Chang KS. Calorimeter ergometer for concentric and eccentric work. Med. Biol. Eng Comput 1981 May;19(3):356-8) has published a concentric/eccentric ergometer, using a 3HP universal motor driving the input of a differential gear of a small import car. Both outputs drive dynamometers, one of them connected to the exercise source.
Fisher (U.S. Pat. No. 4,363,480, Dec. 14, 1982) teaches the use of centrifugally responsive friction brakes in an isokinetic treadmill. Because of the finite gain of a centrifugal regulator, isokinetic operation is achieved only in approximation.
Ruggles (U.S. Pat. No. 4,374,588, Feb. 22, 1983) describes a small frictional exercise device, said to be isokinetic, though speed is not directly controlled; rather, the frictional force is a function of the applied force, by means of a little ball bearings, running in arcuate raceways. It is not truly isokinetic and has limited application.
Mattox (U.S. Pat. No. 4,385,760, May 31, 1983). A slide is confined for travel along a guide having a surface which can be interengaged by one or more friction pads on the slide. An operating lever rigid to the slide and projecting outwardly therefrom may be grasped at its outer end for the purpose of operating the slide, and because the slide is loosely confined on the guide, the user-applied force on the lever rocks the slide in a direction to press the friction component or components tightly against the cooperating surface of the guide to produce frictional resistance as the slide travels along the guide. The pads may be adjustably positioned in any one of a number of locations for achieving variation in resistance generated by the exerciser, and the lever is itself extensible for adjustment of the moment arm between the end of the lever and the surface of the surface engaged by the friction pads. A variety of embodiments are disclosed including a rectilinear form and a curvilinear form.
McCartney (McCartney N, Heigenhauser GJF, Sargeant A J, Jone NL. A constant velocity cycle ergometer for the study of dynamic muscle function. J Appl. Physiol. Respir. Environ Exerc. Physiol 1983; 55(11):212-7) describes a motor driven cycle ergometer. Here the whole power is absorbed in a 3HP DC motor with regenerative control, which makes the apparatus very expensive.
Marczewski (U.S. Pat. No. 4,466,612, Aug. 21, 1984). A variable resistance exercising device is described for executing isometric, isotonic and isokinetic exercises. The device includes a unitary, open-ended mandrel or bar which is shaped to define at least one shaft which is adapted to receive several turns of rope thereon, an open support loop for the rope situated near one end of the shaft, and an open guide loop at the other end of the shaft for holding the rope in proper engagement with the shaft. By virtue of the mandrel's open-ended construction, the rope may be easily engaged or disengaged from the device, and the resistance provided by the device may be changed quickly.
Boettcher (U.S. Pat. No. 4,565,368, Jan. 21, 1986). An isokinetic exercise and monitoring machine for use in exercising and evaluating an individual's back muscles. A preferred embodiment comprises a restraining means for sandwiching the lower body half that is adjustably connected to a support frame a restraining means for sandwiching the upper body half, including means for pivoting the upper body restraining means about the lower body restraining means in response to the individual's movement generated by extension and flexion of his back muscles' a spring-loaded stop to prevent overtravel and excessive deceleration of the second restraining means at the end of its rotational movement, means for vertically adjusting a platform upon which the individual stands so that the restraining means and engage his body appropriately; and wheels and attached to a support frame to provide portability of the machine. The lever arm of a dynamometer attaches to a central point of the upper body restraining means to prevent twisting of the lever arm and problems caused thereby.
Krukowski (U.S. Pat. No. 4,628,910, Dec. 16, 1986). A muscle exercise and rehabilitation apparatus comprises a movable arm against which a force can be applied; a servo motor mechanically coupled to the arm through a gear reducer; a sensing device for sensing the force applied to the arm and for producing a load signal corresponding thereto; a tachometer for producing a velocity signal corresponding to the velocity of the arm; a closed loop velocity servo feedback circuit for controlling the motor in response to a control signal and the velocity signal so that the arm has a constant resistive torque applied thereto and/or has its velocity regulated, regardless of the force applied to the arm, the feedback circuit including an amplifier for amplifying the load signal to produce the control signal, a torque control circuit and a speed clamp circuit for modifying the control signal of the amplifier to produce a modified control signal, depending on the mode of operation; a switch for switching in at least one of the torque control circuit, the speed clamp circuit, an eccentric circuit which controls eccentric operation and an oscillator circuit, and a PWM amplifier for producing an error signal in response to the modified control signal and the velocity signal to control the motor to regulate the velocity of the arm and/or apply a constant resistive torque to the arm, for both extension and flexion, as well as concentric and eccentric operation, regardless of the force applied to the arm.
McArthur (U.S. Pat. No. 4,637,607, Jan 20, 1987). A drive unit for providing kinetic frictional resistance to an exercising apparatus which includes a sub-frame with a driving and driven element coupled to the sub-frame a motor coupled to the driving element for rotatably driving the latter. The driving and driven elements are coupled such that the driving and driven elements slip relative to one another. An adjustment is provided for adjusting the kinetic friction force between the driving and driven elements, while a stop is mounted on the sub-frame for blocking the driven element from movement beyond a start position. In operation the driving element is continuously driven by the motor throughout an exercise so that only kinetic friction has to be overcome by a user.
Bloemendaal (U.S. Pat. No. 4,645,199, Feb. 24, 1987). An exercise device includes a rotor which rotates upon action of an operator. Resistance to rotation of the rotor is provided by fluid trapped between the rotor and a non-rotating portion of the device. A friction relief mechanism provides periodic variation in the amount of resistance to rotation as the rotor is rotated. A fluid level adjustment mechanism permits control of the amount of fluid positioned between the rotor and the non-rotating portion of the device. As the amount of fluid between the rotor and the non-rotating portions of the assembly is increased, the total amount of energy required to complete a single revolution of the rotor is generally increased. In a preferred embodiment, the device is an exercise cycle operated by pedaling. The friction relief mechanism operates so that when the pedaler has pedals positioned at vertical extremes, resistance to pedaling is least; and when the pedals are positioned substantially halfway between the vertical extremes, resistance to pedaling is at a maximum. This periodic variation in the a mount of energy required for rotation, caused by the friction relief mechanism, generally matches a profile of a normal bicycle pedaler's muscle capabilities and output.